Administration of triiodothyronine and dopamine to broiler chicks increases growth, feed conversion and visceral organ mass

The influences of triiodothyronine (T3) or dopamine (DA) administration on growth, feed conversion, and visceral weights in broiler chicks between the ages of 6 and 12 d posthatch were investigated. In Trial 1, six chicks at age 6 d were randomly administered one of the following treatments: 0.37, 0.74, 1.48, and 2.96 micromol T3/kg BW or 0.07, 0.14, 0.28, and 0.56 micromol DA/kg BW. Both T3 and DA were administered via intraperitoneal injections between the end of sternum and the ends of os pubis, with 0.9% saline as the excepient. In addition, two groups of six birds each were either not injected or injected with excepient only, as controls. Four replications were carried out with a total of 264 chicks. Heart weight as a percentage of feed-deprived body weight (FDBW) of the chicks injected with 2.96 micromol T3/kg BW was heavier than that of controls. Other variables measured were not significantly different between treatments. In trial 2, six chicks at age 6 d were randomly administered, one of the following treatments: 0.56, 1.12, 2.24, and 4.48 micromol T3/kg diet or 0.40, 0.80, 1.60, and 3.20 micromol DA/kg diet as well as a nonsupplemented control. Four replications were carried out with 216 chicks. The results in Trial 2 showed that the effects of T3 (X, micromol/kg diet) on body weight gain (Y1, g) and feed consumption (Y2, g) were linear (Y1 = 310 - 21.5X, R2 = 0.868, P < 0.001 and Y2 = 398 - 22.3X, R2 = 0.765, P < 0.001, respectively). The feed conversion ratio, the weight of liver, the weights of various intestinal segments, the lengths of the duodenum, jejunum and the ileum, as well as weight per centimeter jejunal length, gizzard weight as percentage of FDBW, and the duodenal length per kilogram FDBW all had linear responses (P < 0.05) to the level of dietary supplementation of T3. The effect of dietary supplementation of T3 on the heart weight was quadratic (Y16 = 2.58 + 0.89X - 0.17 X2, R2 = 0.526, P < 0.01). Similarly, the weights of pancreas and gizzard, the heart weight as a percentage of FDBW and the pancreas weight as a percentage of FDBW all had second-order curve responses. Dietary DA supplementation exerted no effect on the variables measured except that the regression of the heart weight as a percentage of FDBW on dietary DA supplementation (X1, micromol/kg diet) existed, namely, Z1 = 0.64 + 0.24 X1 - 0.23 X1(2) + 0.05 X1(3) (R2 = 0.868, P < 0.05).

Suramin protects the murine motor nerves from the toxic effects of presynaptic Ca(2+) channel inhibitors

The purpose of this study is to investigate whether suramin is capable of preventing the neurotoxic effects of Ca(2+) channel inhibitors at the presynaptic sites. Mouse diaphragm and triangularis sterni preparations were used for this study in order to measure the muscle tension and nerve terminal Ca(2+) current, respectively. Both omega-conotoxin MVIIC and omega-agatoxin IVA markedly inhibit the nerve-evoked muscle contractions as well as the nerve terminal Ca(2+) current respectively. Pretreatment with suramin (0.3 mM) significantly reduced the inhibitory effect of nerve-evoked muscle contractions and Ca(2+) current induced by either omega-conotoxin MVIIC or omega-agatoxin IVA but not that induced by the non-selective Ca(2+) channel blocker, Cd(2+). Neither suramin nor Ca(2+)-channel toxins significantly affect Na(+)- and K(+) currents of the nerve terminals. These findings indicate that suramin selectively interferes the action of presynaptic Ca(2+) channel neurotoxins and thus reduces their depressant effects on the muscle contractions. The implication of these findings is that suramin and its derivatives may potentially become useful agents in management of intoxication of Ca(2+) channel neurotoxins.

Effects of Scutellarein on diabetic rat aorta

AIM

To study the effect of Scutellarein (Scu) on the diabetic rat aorta.

METHODS

Contractile responses to phenylepherine and endothelium-dependent relaxation responses to acetylcholine (ACh) in rat aorta were investigated after streptozocin-induced 6-wk diabetes, Scu-treated streptozocin-induced diabetes, and in age-matched control in vitro.

RESULTS

1) Endothelium-dependent relaxation to ACh in diabetic rats was decreased (P < 0.01) compared with age-matched control. 2) Contractile responses to phenylepherine were increased (P < 0.01) in diabetic rats. 3) The dietary supplement of 0.5% Scu starting from 1-wk diabetes induction prevented endothelial dysfunction (P < 0.01), but the contractile responses to phenylepherine were further increased.

CONCLUSION

Scu prevented vascular endothelial dysfunction in diabetic rats, and also potentiated the contraction induced by phenylepherine.

One-codon alternative splicing of the CpG MTase Dnmt1 transcript in mouse somatic cells

The genomic methylation patterns in the mammalian somatic cells are presumably maintained by a single enzyme, dnmt1. In mouse, this DNA (cytosine-5)-methyltransferase, or CpG MTase, is encoded by the Dnmt1 gene. We now present evidence that in different tissues and cell types, the primary transcript of mouse dnmt1 is alternatively spliced to generate two poly-(A) RNAs of approximately similar abundance. This alternative splicing most likely originates from the existence of two tandemly arranged acceptor sites separated by only 3 nt. The two Dnmt1 mRNAs thus encode two CpG MTases differing by two amino acids. We discuss the implications of the discovery of two dnmt1 isozymes, instead of one enzyme as previously thought, in the somatic cells of both mouse and human.

Erigeron breviscapus prevents defective endothelium-dependent relaxation in diabetic rat aorta

We examined the endothelium-dependent relaxation response to acetylcholine (Ach) in streptozotocin-induced diabetic rat aorta at the stages of 2- and 6-wks' duration in vitro, and compared with another two groups which were treated with dietary supplement of 0.1% Aminoquanidine (AG) and 0.5% Erigeron breviscapus (EB) from 1-week of diabetes induction. At the stage of 2-wks' duration of diabetes, relaxation responses to lower concentrations of Ach in 0.3 uM phenylepherine-precontracted aortas were diminished significantly (P<0.05) compared with age-matched control, but the maximal relaxation of Ach remained unchanged. At the stage of 6-wks' duration, diabetes caused an approximately 60% (P<0.001) deficit in maximum relaxation, and this was significantly (P<0.001) prevented in AG and EB treated groups. There was an approximately 40% enhancement in the maximum contractile response to phenylepherine with diabetes (P<0.05), which was unaffected significantly by AG and EB treatments. The data suggest that the defective endothelium-dependent relaxation in diabetic rat aorta occurred as early as 2-wks' duration of diabetes, and the treatments of AG and EB could protect vascular endothelium although the deficits in vascular smooth muscle contractile responses were not protected.

Suramin inhibits the toxic effects of presynaptic neurotoxins at the mouse motor nerve terminals

Clinically available chemical antagonists of snake neurotoxins still await to be identified. In this study, we demonstrate that an anti-trypanosomiasis agent, suramin, is an effective inhibitor of beta-bungarotoxin isolated from the venom of Formosan Krait snake. Following intraperitoneal injection (12 ng/g) of beta-bungarotoxin in mice, the time to paralysis (loss a limb withdrawal reflex, 21. 8+/-3.4 h, n=4) was significantly prolonged after intravenous injection (16 microg/g) of suramin (35.9+/-4.0 h, n=4, P<0.05). The mechanism of this inhibitory effect of suramin was analyzed at the mouse nerve terminals. beta-Bungarotoxin (1 microg/ml) produces an irreversible blocking effect of nerve-evoked muscle contractions of mouse phrenic nerve-diaphragm (blocking time 135+/-6 min, n=6). Pretreatment with suramin (0.3 mM) significantly prolonged the blocking time by three-fold. This selective inhibitory effect of suramin was further confirmed when suramin was shown to delay the neuromuscular blocking effect of another presynaptic neurotoxin, crotoxin (from American rattlesnake venom), but not that of the postsynaptic neurotoxin, alpha-bungarotoxin. Furthermore, suramin inhibited beta-bungarotoxin in blocking transmitter release as revealed by prolonging the time to abolish the end-plate potential amplitude (with suramin, 391+/-8 min; without treatment, 141+/-5 min). K(+) current was measured in the mouse triangularis sterni preparation; suramin (0.3 mM) had no significant effect on beta-bungarotoxin in inhibiting K(+) current (77+/-3% of control; with suramin 75+/-3% of control, respectively). These findings clearly show that suramin is an inhibitor of presynaptic neurotoxins, mediated by interrupting the toxins in blocking the releasing mechanism of transmitter at the motor nerve terminals. The implication of these findings is that suramin and related compounds can become useful agents in management of snakebites.

Two major forms of DNA (cytosine-5) methyltransferase in human somatic tissues

Thus far, only one major form of vertebrate DNA (cytosine-5) methyltransferase (CpG MTase, EC 2.1.1.37) has been identified, cloned, and extensively studied. This enzyme, dnmt1, has been hypothesized to be responsible for most of the maintenance as well as the de novo methylation activities occurring in the somatic cells of vertebrates. We now report the discovery of another abundant species of CpG MTase in various types of human cell lines and somatic tissues. Interestingly, the mRNA encoding this CpG MTase results from alternative splicing of the primary transcript from the Dnmt1 gene, which incorporates in-frame an additional 48 nt between exons 4 and 5. Furthermore, this 48-nt exon sequence is derived from the first, or the most upstream, copy of a set of seven different Alu repeats located in intron 4. The ratios of expression of this mRNA to the expression of the previously known, shorter Dnmt1 mRNA species, as estimated by semiquantitative reverse transcription-PCR analysis, range from two-thirds to three-sevenths. This alternative splicing scheme of the Dnmt1 transcript seems to be conserved in the higher primates. We suggest that the originally described and the recently discovered forms of CpG MTase be named dnmt1-a and dnmt1-b, respectively. The evolutionary and biological implications of this finding are discussed in relation to the cellular functions of the CpG residues and the CpG MTases.

[Role of caudal pressor area of medulla oblongata in vasomotor tone of peripheral vessels]

To study the role of the caudal pressor area (CPA) on the ventral surface of medulla oblongata in vasotonia of the skeletal muscles and kidneys, perfusion pressures of vessels in skeletal muscles and kidneys were recorded to observe effects of microinjection of L-glutamate (L-glu) into CPA. The results are as follows. L-glu induced a significant increase of artery pressure (AP), perfusion pressure of muscles (PPm) and perfusion pressure of kidney (PPk), which was markedly attenuated by prior injection of phentolamine or propranolol to the bilateral pressor area. These results indicate that the vascular roles of CPA were mainly mediated via alpha- and/or beta-receptors.

Enhanced spontaneous transmitter release at murine motor nerve terminals with cyclosporine

Cyclosporine, a calcineurin inhibitor, significantly enhances spontaneous acetylcholine release after a brief tetanus and potentiates the effect of phorbol 12,13-dibutyrate. Both actions are prevented by the protein kinase C inhibitor, bisindolylmaleimide iodide. Protein kinase C and calcineurin thus play important roles in the balance between phosphorylation and dephosphorylation regulating spontaneous transmitter release at motor nerve terminals.

Inhibitory effects of S-nitrosocaptopril on vasomotor tone

AIM

To study effects of captopril (Cap) and S-nitrosocaptopril (CapNO) on vascular tension.

METHODS

Tension of rabbit aortic rings and perfusion pressure of rat renal artery (PPr) were examined to evaluate the effects of CapNO.

RESULTS

CapNO (3 nmol.L-1-10 mumol.L-1) produced concentration-dependent vasorelaxation response in the rings of rabbit thoracic aortas. Endothelium denudation did not alter the relaxations to CapNO. In contrast, Cap had no vasorelaxing effect on the rings precontracted with phenylephrine. CapNO (10 nmol.L-1) decreased rat PPr in vivo (P < 0.01), and the effect was concentration-dependent and reversible. Cap showed a reduction in rat PPr only at the concentration 1000 nmol.L-1 (P < 0.05). The relaxing potency of CapNO was 100 times higher than that of Cap in this respect. Pre-perfusion of rat renal arteries with NG-monomethyl-L-arginine monoacetate (L-NMMA, 0.03 nmol.L-1) or L-arginine (3 nmol.L-1) did not significantly blocked the relaxing effect induced by CapNO.

CONCLUSION

CapNO had a direct vasodilatory effect.

Phorbol ester-induced contractions of mouse detrusor muscle are inhibited by nifedipine

The effects of phorbol esters on contractions of detrusor strips isolated from mouse urinary bladder were studied. Beta-phorbol-12,13-dibutyrate (beta-PDBu, 10 nM) significantly enhances both the neurogenic and myogenic detrusor contractions to a similar extent. By contrast, an inactive isoform of protein kinase C (PKC) stimulation, alpha-phorbol-12,13-dibutyrate (100 nM) has no such enhancing effect on the muscle contraction. The effect of beta-PDBu was dependent on the extracellular Ca2+ concentration. Nifedipine (0.3 microM, a L-type Ca2+ channel blocker), staurosporine (1 microM) and bisindolylmaleimide I (microM, a selective PKC inhibitor) but not omega-conotoxin GVIA (an N-type Ca2+ channel blocker) abolished the enhancing effect of beta-PDBu. In other words, beta-PDBu failed to augment the nifedipine-insensitive component of the muscle contraction. Moreover, beta-PDBu not only enhances the muscle response induced by exogenous agonists (acetylcholine or ATP) and KCl but also increases the resting tone of detrusor muscle, an effect which is also inhibited by nifedipine and bisindolylmaleimide I. From these findings, it is concluded that the enhancing effect of beta-PDBu is due to activation of the L-type Ca2+ channel through phosphorylation by protein kinase C. This allows more Ca2+ influx from the extracellular medium, leading to an increase in the contractions of the mouse detrusor muscle.

Comparison of serum fructosamine vs glycohemoglobin as measures of glycemic control in a large diabetic population

In diabetic patients, measurement of glycohemoglobin (HbA1C) is widely accepted as the standard method for determining long-term glycemic control. Another test, the serum fructosamine test, has been suggested as a less costly alternative. To compare these two tests, we evaluated how well each correlated with fasting blood glucose and how well each could predict the degree of glycemic control perceived by treating physicians. Among 222 diabetic subjects, fructosamine (r=0.74) and fructosamine corrected for serum albumin (c-fructosamine) (r=0.79) correlated better with fasting blood glucose than did HbA1C (r=0.68) (P<0.05). Among 450 diabetic subjects, fructosamine, c-fructosamine, and HbA1C showed similar error rates (23%-26%) when discriminating between subjects who had either poor vs not-poor control or poor-to-fair versus good-to-excellent control. However, receiver operating characteristic curves for these tests indicated that HbA1C was the best discriminator because it showed a 9% to 10% greater area under the curve (P<0.05).

Studies on curare-like action of the tripeptide carbobenzoxy-Gly-Gly-Arg-beta-naphthylamide in mouse diaphragm

The effects of several protease substrates or protease inhibitors on neuromuscular transmission in the isolated mouse phrenic nerve-diaphragm were studied. N-Carbobenzoxy-Gly-Gly-Arg-beta-naphthylamide (Z-GGR-N) but none of the other agents inhibited the nerve-evoked muscle contractions. By means of electrophysiological studies, Z-GGR-N was found to inhibit the amplitudes of both end-plate potentials (epps) (IC50 approximately 50 microM) and miniature end-plate potentials (mepps) but to increase the frequencies of mepps. This tripeptide could protect the nicotinic acetylcholine receptor from the irreversible inhibitory action of alpha-bungarotoxin on the mouse diaphragm. Similar to D-tubocurarine, Z-GGR-N induced tetanic fading both of nerve-evoked muscle contractions and of the amplitude of epps. Furthermore, Z-GGR-N exhibited a greater depression of the amplitudes of train-epps than those of mepps, similar to that of hexamethonium and D-tubocurarine, indicating an effect on presynaptic autoreceptors. Suramin, which could competitively reverse the inhibitory effects of non-depolarizing relaxants, acted in this study as an antagonist of all the effects of Z-GGR-N, especially those at the presynaptic site. All of these findings suggest that Z-GGR-N is a novel tripeptide possessing curare-like actions at both presynaptic and postsynaptic sites and that these actions are independent of its protease substrate property.

'Best clinical practice': assessment of processes of care and of outcomes in the US Military Health Services System

The National Quality Management Program of the Military Health Services System of the United States has undertaken a series of projects whose objective is the active, on-going monitoring and improvement of the effectiveness and efficiency of the care provided to a broad population that encompasses troops on active duty, retirees and dependents. The analytic activities consist of (1) identification by clinical panels of conditions and procedures of interest; (2) collection of data from electronic repositories and from charts to characterize the patients, how they are managed, the clinical outcomes they experience, the resource costs their care entails, and, from questionnaires, their functional status and level of satisfaction, and (3) generation of 'report cards' that inform organizational units down to the level of the hospital of the characteristics of their patients, their practices, and the risk-adjusted outcomes they achieve. The patterns of care employed by the hospitals that obtain the best risk-adjusted outcomes and resource utilization ('best clinical practice') are identified and made known. In addition, (4) a systematic process of developing outcomes-based practice guidelines has been devised. It intent is to serve as a decision-support tool for clinicians. Initial estimates have been obtained of the probable consequences of the application of this tool to operative interventions in childbirth. Use of the tool would result in a higher occurrence of elective Caesarean sections, a reduced rate of emergency Caesarean sections and much lower use of forceps, with an overall improvement in outcomes and lower resource costs. This program is currently in the early phases of implementation. The two principal requirements for the immediate future are (1) education of the clinical and administrative communities in the use of the data and the decision-support tools and (2) evaluation of the consequences of the use of the data by the clinical and administrative communities.

Involvement of nitric oxide in the in vivo effects of lipopolysaccharide on the contractile and electrical properties of mouse diaphragm

The contractile and electrical properties of the mouse diaphragm during endotoxemia were studied, and the possible role of nitric oxide (NO) on these changes was investigated. The mice were injected intraperitoneally with E. coli. lipopolysaccharide (endotoxin, LPS) at various times before isolation of the diaphragm to induce endotoxemia. It was observed that direct twitch tension was slightly increased, and that there was a significant increase in tetanic tension when compared with controls. The potentiation of direct twitch tension induced by a Cl--channel blocker (9-anthracene carboxylic acid), but not the potentiation by a Na+-channel activator (veratridine) or by K+-channel blockers (uranyl ion, 4-aminopyridine and tetraethylammonium ion), was attenuated in the diaphragm of LPS-treated mice. Moreover, the resting membrane potential was significantly reduced and the membrane input resistance was significantly increased, largely due to a decrease in Cl--conductance. However, the membrane K+-conductance remained unaltered. These results imply that the sarcolemmal Cl--channel is markedly affected in the mouse diaphragm during endotoxemia. These changes of contractile and electrical characteristics of the mouse diaphragm during endotoxemia could be reversed by treatment with dexamethasone and N(G)-nitro-L-arginine (NO synthase inhibitors). On the other hand, in in vitro studies, LPS (20 microg/ml), by itself, applied directly to the diaphragm, did not alter the muscle contractions or the membrane potentials. A NO donor, added to the diaphragm bath, increased the tetanus/twitch ratio and induced a transient depolarization. All of these findings suggest that LPS may, at least in part, affect the sarcolemmal electrical properties and muscle contractions during endotoxemia through the L-arginine:NO pathway.

A potential determinant of enhanced crystallization of Hbc: spectroscopic and functional evidence of an alteration in the central cavity of oxyHbC

The structural basis of the crystallizing tendencies of oxyHbC (beta 6Glu-->Lys), that produces haemolytic anaemia in homozygotes, is unknown. Using a fluorescent organic phosphate analogue (8-hydroxy-1,3,6-pyrenetrisulphonate), and conventional oxygen equilibrium studies, data suggest that the binding of inositolhexaphosphate (IHP) to oxyHbC differs from HbA, indicating perturbations of the oxyHbC central cavity, which was predicted from our earlier spectroscopic findings. To define the relationship between this conformational change in oxyHbC and its tendency to crystallize, the effect of four central cavity ligands on the crystallization rate was studied: a peptide containing 11 residues from the N-terminal portion of band 3, the full cytoplasmic domain of band 3, 2,3-diphosphoglycerate and IHP. OxyHbC crystallization was accelerated by all these central cavity ligands and not by the appropriate controls. These central cavity changes become an excellent candidate for the dramatic increase in the crystallization rate of oxyHbC.

HbC compound heterozygotes [HbC/Hb Riyadh and HbC/Hb N-Baltimore] with opposing effects upon HbC crystallization

Compound heterozygotes of variant haemoglobins (Hbs) with HbC, with or without novel phenotypic changes, have provided insight into the molecular basis of the interacting haemoglobins and information concerning the role of specific residues in the crystallization of oxy HbC. A high phosphate buffer system has proved useful for studying the effects of variant haemoglobins (naturally co-existing with HbC in the red cell) on the oxy HbC crystallization process and has led us to conclude that beta87 and beta73 are contact sites of the oxy HbC crystal. We now present investigations from two HbC compound heterozygotes which exhibit opposing effects upon HbC crystallization: HbC/Hb N-Baltimore (beta95 Lys-->Glu) and HbC/Hb Riyadh (beta120 Lys-->Asn). The latter inhibits the in vitro crystallization of HbC, explaining the lack of erythrocyte abnormalities (with the exception of microcytosis) in the doubly heterozygous infant. In contrast, Hb N-Baltimore accelerates the crystallization of HbC, contributing to multiple abnormalities in red cell morphology, albeit in the absence of morbidity. We conclude that (1) beta120 and beta95 are additional contact sites in the crystal, and (2) the HbC/Hb Riyadh haemoglobinopathy demonstrates that crystallization may not be required for the generation of the observed microcytosis and increased red cell density in HbC-containing red cells.

Multiple types of Ca2+ channels in mouse motor nerve terminals

We measured neurotransmitter release and motor nerve terminal currents in mouse phrenic nerve-diaphragm and triangularis sterni preparations, to evaluate the role of Ca2+-channel subtypes in regulating transmitter release. Saturated concentrations of either omega-agatoxin IVA [omega-Aga-IVA (0.3 microM), a blocker of P-type Ca2+ channels] or omega-conotoxin MVIIC [omega-CTx-MVIIC (2 microM), a P- and Q-type Ca2+-channel blocker], inhibited nerve-evoked muscle contractions and the amplitude of endplate potentials respectively. In contrast, combined treatment with nifedipine (50 microM, a blocker of L-type Ca2+ channels) plus omega-conotoxin GVIA [omega-CTx-GVIA (2 microM), a blocker of N-type Ca2+ channels] did not elicit inhibitory effects on nerve-evoked muscle contractions, endplate potentials or nerve terminal waveforms. Because of the non-linear relationship between endplate potentials and Ca2+ signals, a small decrease in presynaptic Ca2+ entry can significantly reduce the amplitude of the endplate potential. Thus, we applied 3,4-diaminopyridine (3,4-DAP, a K+-channel blocker) or high Ca2+ (10 mM) to accelerate and amplify the endplate potentials and Ca2+ currents. The endplate potentials amplified by 3,4-DAP or by high Ca2+ correspondingly proved to be quite resistant to both omega-Aga-IVA and omgea-CTx-MVIIC; omega-Aga-IVA exerted only a partial inhibitory effect on endplate potentials, and the omega-Aga-IVA-resistant component was further inhibited by omega-CTx-MVIIC. The component that was resistant to the two toxins could be completely blocked by the non-selective Ca2+ channel blocker Cd2+ (300 microM). A combination of the two toxins had no significant effects on either spontaneous transmitter release or postsynaptic resting membrane potentials of the diaphragm preparation and the Na+ and K+ waveforms of the triangularis sterni preparations. This finding suggests a preferential inhibitory effect at a presynaptic site. Measuring the Ca2+ currents in the triangularis sterni also revealed partial inhibition by omega-CTx-MVIIC with further incomplete inhibition by omega-Aga-IVA. Cd2+ (300 microM) abolished the toxin-resistant component of the Ca2+ current. In contrast, a combination of nifedipine (50 microM) with omega-CTx-GVIA (2 microM) was without inhibitory effect. We conclude that multiple types of Ca2+ channels, i.e. omega-Aga-IVA-sensitive, omega-CTx-MVIIC-sensitive and toxin-resistant Ca2+ channels, coexist in mouse motor nerve terminals.

Hb Montefiore (126(H9)Asp-->Tyr). High oxygen affinity and loss of cooperativity secondary to C-terminal disruption

Hb Montefiore was found, in the heterozygous state, in a Puerto Rican female who had a slightly elevated total Hb level. Structural analysis revealed that Asp-alpha126 was replaced by Tyr. Hb Montefiore migrates close to HbF (at pH 8.6) and accounts for 20.3% of the hemolysate. Oxygen binding of red blood cells revealed a 40% decrease in the P50 (pH 7.4) and a low n value of 1.6 (normal: 2.6). Depletion of red blood cell 2,3-DPG did not change the results. Stripped Hb Montefiore at pH 7.2 showed an 8-fold reduction in P50 (0.6 versus 4.6 mm Hg) and very low cooperativity (n = 1.2 versus 2.9 for the control). Heterotopic effectors, as 2,3-diphosphoglycerate and inositol hexaphosphate had a normal effect and in addition, they increased cooperativity. The chloride ion effect and the Bohr effect were moderately reduced. A bezafibrate derivative (L345), known to bind alpha126, increases the P50 of HbA by 9-fold, but only by 1. 5-fold that of Hb Montefiore. Combining these functional studies with intrinsic fluorescence and Resonance Raman spectroscopy, we interpret the very low n value and the high oxygen affinity for Hb Montefiore as a result of both a destabilized T state that switches to R upon ligand binding and a deoxy T state that binds ligands with higher affinity than that of deoxy HbA. Hb Montefiore still binds ligands cooperatively, but the difference in ligand binding properties of the two quaternary states has been drastically reduced.

Ruthenium red, a novel enhancer of K+ currents at mouse motor nerve terminals

The effects of ruthenium red (RR) on transmitter release and pre-synaptic currents were studied in the mouse neuromuscular junction. The action of RR (10 microM) was shown not only in the complete suppression of nerve-evoked muscle contractions associated with the depression of endplate potential amplitude but also in the partial inhibition of the amplitude of miniature-endplate potentials. However, the other ruthenium compounds, ruthenium chloride and tris (2,2-bipyridyl) ruthenium chloride did not significantly affect the neuromuscular transmission. In pre-synaptic waveform studies, the fast K(+)-current [IK(f)] as well as the ca(2+)-activated K(+)-current [IK(ca)] was significantly enhanced by 10 microM RR. Furthermore, 10 microM RR antagonized the action of beta-bungarotoxin (a blocker of slow K(+)-channel [IK(s)] in enhancing pre-synaptic Ca2+ currents. In contrast, the typical Ca(2+)-channel blockers, omega-agatoxin (0.5 microM), Gd3+ (0.5 mM) and CD2+ (0.3 mM) all suppressed the IK(ca). Although RR (1-30 microM) inhibited the Ca(2+)-currents of the nerve terminals induced by the combined treatment with the K(+)-channel blockers, 3,4-diaminopyridine plus tetraethylammonium chloride in a concentration-dependent manner, it is considered that RR-enhanced K+ currents were responsible for, at least in part, the observed inhibition of the Ca(2+)-current which led to the blockade of transmitter release.

Technical performance evaluation of BM/Hitachi 747-200 serum fructosamine assay

The technical performance of serum fructosamine assay as a short-term index of diabetic control was evaluated by using the BM/Hitachi 747-200 Automatic Analyzer (Boehringer Mannheim Corp). Intra- and interassay precisions (CV) were <2%. Linearity was confirmed up to 1000 micromol/L. Lipemia, produced artificially or from hypertriglyceridemia in vivo, did not interfere with measurement of serum fructosamine concentration. However, hemoglobin (Hb) interfered with measurement substantially at concentrations >15.5 micromol/L, and bilirubin interfered substantially at concentrations >68.4 micromol/L. A normal reference range of up to 282 micromol/L (mean +/- 2SD = 242 +/- 40) was derived from results obtained from 228 nondiabetic subjects. In 222 diabetic subjects, serum fructosamine concentration correlated well with fasting glucose concentration (r = 0.74) and with Hb A1c concentration (r = 0.80). This automated fructosamine assay has the advantages of technical simplicity, low cost, and reduced analytical time compared with the Hb A1c method.

Technical performance evaluation of BM/Hitachi 747-200 serum fructosamine assay

The technical performance of serum fructosamine assay as a short-term index of diabetic control was evaluated by using the BM/Hitachi 747-200 Automatic Analyzer (Boehringer Mannheim Corp). Intra- and interassay precisions (CV) were &lt;2%. Linearity was confirmed up to 1000 micromol/L. Lipemia, produced artificially or from hypertriglyceridemia in vivo, did not interfere with measurement of serum fructosamine concentration. However, hemoglobin (Hb) interfered with measurement substantially at concentrations &gt;15.5 micromol/L, and bilirubin interfered substantially at concentrations &gt;68.4 micromol/L. A normal reference range of up to 282 micromol/L (mean +/- 2SD = 242 +/- 40) was derived from results obtained from 228 nondiabetic subjects. In 222 diabetic subjects, serum fructosamine concentration correlated well with fasting glucose concentration (r = 0.74) and with Hb A1c concentration (r = 0.80). This automated fructosamine assay has the advantages of technical simplicity, low cost, and reduced analytical time compared with the Hb A1c method.